Single-photon absorptiometry has been widely used for measurement of bone mineral content in vivo and dual-photon absorptiometry is now being used for measurement of spinal and total-body mineral. Reproducibility and speed of these measurements can be greatly increased using linear or area detectors. We are developing and testing proportional counters for use as linear or area detectors. These counters use resistive anodes and timing electronics. High-efficiency is achieved by using xenon at 5 to 30 atm pressure. We are optimizing the design of such detectors to provide high count rates (1 mHz), high resolution (1 to 2 mm), and high efficiency (over 50%). Several linear detectors were constructed in cooperation with Oak Ridge National Laboratory. These are being tested for absorptiometry determinations of bone mineral.